In some aircraft, warm air may be channeled from an electrical equipment (E/E) bay to a cargo bay in order to heat the cargo bay using two fans. Specifically an upstream fan, which may be an E/E fan, pulls the warm air from the E/E bay. A downstream fan, which may be a forward cargo air conditioning (FCAC) fan, forces the warm air into the cargo bay. The upstream fan and the downstream fan may be fluidly coupled to one another by a duct.
Sometimes the upstream fan may be powered before the downstream fan. The operation of the upstream fan forces the warm air through the duct and towards the downstream fan before power is supplied to the downstream fan. The warm air may cause the downstream fan to rotate in an unpowered state, which is also referred to as windmilling. This windmilling may interfere with the ability to eventually supply power to the downstream fan. Specifically, the windmilling of the downstream fan may cause a rotor located within an electric motor to also spin, thereby causing the electric motor to operate as a generator. When power is initially supplied to the electric motor by a controller, a current imbalance may be created if the electric motor is operating as a generator. The controller may cease to supply power to the electric motor once the current balance is detected, and the downstream fan is no longer powered.
In one approach, the controller may include additional control logic or circuitry in order to account for the spinning of the rotor and the current imbalance that is generated within the electric motor when the downstream fan is windmilling. However, the additional circuitry or control logic may increase the cost and complexity of the overall ventilation system. In another attempt to solve the above-described issue, an aperture or gap may be located along the duct between the upstream fan and the downstream fan. The aperture may allow a portion of the warm air to escape from the duct before reaching the downstream fan. However, this approach is not considered to be an effective solution because the gap may not allow for a sufficient amount of warm air to escape the duct in order to substantially prevent the downstream fan from windmilling. Thus, there exists a continuing need in the art for an effective yet economical solution that allows the downstream fan to receive initial power after the upstream fan is turned on.